Oxidation mechanism of a near β-Ti alloy

Near β-Ti alloys, a perfect candidate material for numerous applications in the aerospace, are expected to exhibit high temperature endurability. Here, in order to evaluate the high temperature oxidation mechanism of the near β-Ti alloy, detailed microstructural characterization was performed on a near β-Ti alloy, Ti-55511 alloy after isothermal heat treatment at 600 °C in a tube furnace. Parabolic oxidation kinetics was observed. The oxide layer consisted of Al2O3, TiO2, VO2, and Magnéli phases. Polymorphic phase transformations and Magnéli phases played critical roles in the oxide layer thickening. The formation of defects was highly correlated with the incorporation of oxygen into Al2O3 and VO2, which resulted in lattice distortion of the oxides. Continuous oxidation led to the formation of the higher-valence oxide V2O5 in VO2 particles.